Heat waves and peak UV levels: why daily sun protection is non-negotiable

Heat waves are no longer exceptional events. As a result of climate change, heat waves are becoming more frequent, intense, and prolonged: in France, before 1989, they occurred on average once every five years, compared to nearly every year since 2000. These periods of intense sunshine are inevitably accompanied by high levels of ultraviolet radiation and more frequent and prolonged skin exposure.

In this context, a simple gesture takes on special significance. As episodes of intense heat and strong sunlight become more frequent, daily skin protection is no longer just an occasional precaution, but the foundation of a consistent routine. That is the whole point of the "PROTECT" step in the PERS method, which is based on two complementary actions: broad-spectrum sun protection and an antioxidant such as vitamin C.

More frequent heat waves, increasing sun exposure

Heat waves are not simply a matter of perceived temperature. They correspond to periods of intense sunshine, during which the UV index reaches high levels for several hours and over several consecutive days. Repeated exposure—which is often underestimated during daily activities—increases the amount of radiation the skin receives over time.

This reality changes the way we think about sun protection. It’s not just about protecting yourself during prolonged exposure at the beach, but about treating sun protection as part of your daily skincare routine—applied every morning, even on cloudy days, since UVA rays penetrate clouds and glass.

Why UV Rays Accelerate Skin Aging

Ultraviolet radiation is the primary environmental factor in so-called extrinsic skin aging. UVB rays, which are absorbed mainly by the superficial layers of the skin, cause erythema and changes in the epidermis. UVA rays, which have a longer wavelength, penetrate deeper into the dermis and interact with the skin’s supportive structures.

At the cellular level, UV exposure generates reactive oxygen species (free radicals) that promote the breakdown of collagen and elastin, contributing to the development of wrinkles, sagging, and pigmentation spots. Heat itself adds another stressor: research on “thermal aging” has shown that an increase in skin temperature can stimulate the metalloproteinase MMP-1 and reduce procollagen synthesis—two mechanisms involved in the weakening of supportive fibers. During a heat wave, the skin is therefore subjected to combined stress from both oxidative and thermal stress.

Daily sun protection: the best-documented practice

Of all skincare measures, daily sun protection is the one with the strongest scientific evidence for reducing sun-induced skin aging. A landmark randomized trial showed that regular application of sunscreen measurably slowed the appearance of visible signs of aging compared to only occasional use. During periods of extreme heat, when the UV index is high and sun exposure is more frequent, this benefit is even more significant.

According to the PERS approach, effectiveness depends as much on the formula as on consistent application. The PERS Invisible Gel SPF50+ combines broad-spectrum UVA and UVB filters with vitamin E in an invisible, non-sticky formula with a matte finish, designed for daily use. Sunscreen is only effective if it is actually applied every day; user comfort therefore becomes a key factor in its effectiveness.

Vitamin C: Strengthening the Skin's Antioxidant Defense System

Sunscreen protects against UV radiation. Vitamin C, on the other hand, addresses its effects within the skin. It is one of the most extensively studied antioxidants for the skin: it helps neutralize UV-induced free radicals, contributes to collagen synthesis, and helps even out skin tone by regulating melanin production, which helps limit the appearance of dark spots caused by repeated sun exposure.

When applied in the morning, the 10% PERS Vitamin C Serum is part of this approach: it supports the skin’s defense mechanisms against oxidative stress and restores the complexion’s radiance, to be used before applying sunscreen. Its stabilized form of vitamin C is designed to balance effectiveness and skin tolerance in a lightweight texture that absorbs quickly.

SPF and Vitamin C: Two Complementary Mechanisms

The benefit of this routine lies in the complementary nature of these two steps. Formulations combining vitamins C and E have been shown to provide photoprotective action based on a mechanism different from that of sunscreens, capable of supplementing—rather than replacing—the protection provided by sunscreen. In other words, antioxidants do not replace sunscreen, and sunscreen does not render antioxidants unnecessary.

In the morning, the routine is simple and consistent: first apply the antioxidant serum, then the broad-spectrum sunscreen. The former strengthens the skin’s internal defenses, while the latter limits the amount of radiation that reaches it. Together, they form a daily protective foundation that is particularly useful as episodes of intense heat and sunlight become more frequent.

Key Takeaways

The increasing frequency of heat waves serves as a reminder of a sometimes overlooked fact: skin protection is a daily practice, not just something to do during prolonged sun exposure. When faced with high UV levels and heat that puts a strain on the skin, two morning routines form the most effective foundation. Broad-spectrum sunscreen, the most well-documented defense against sun-induced aging. And a vitamin C serum, to boost antioxidant defense and support a radiant complexion. Protecting your skin every morning, without fail, remains the best way to preserve its health over the long term.

Scientific Sources